The use of ultrasonic energy to ablate obstructions within blood vessels has been proposed as a viable alternative to the commonly performed "balloon" angioplasty procedures wherein the occlusive lesion is dilated or compressed by inflation of a transluminally inserted balloon. Ultrasonic ablation may also be used to ablate thrombus within blood vessels.
Methods and apparatus for effecting ultrasonic ablation have been described in the prior art. One type of ultrasonic ablation apparatus known in the prior art comprises a flexible intravascular catheter having an ultrasound transmission wire or waveguide which extends longitudinally therethrough. A probe tip or distal head is formed on the distal end of the ultrasound transmission wire or waveguide. Such probe or distal head may protrude beyond the distal tip of the catheter. The proximal end of the transmission wire or waveguide is connected to an ultrasound generator. Sonic energy is thereby transmitted through the transmission wire causing the distal head or probe of the device to undergo vibratory movement. Such vibratory movement of the distal head or probe has been demonstrated to cause ablation of vaso-occlusive atherosclerotic lesions without damaging or perforating the surrounding blood vessel wall.
Examples of ultrasonic ablation devices and related apparatus used in the performance of ultrasonic angioplasty devices include those described in U.S. Pat. Nos. 3,433,226 (Boyd), 3,823,717 (Pohlman et al.), 4,808,153 (Parisi), 4,936,281 (Stasz), 3,565,062 (Kuris), 4,924,863 (Sterzer), 4,870,953 (DonMichael et al.); and other Patent Publications WO87-05739 (Cooper), WO89-06515 (Bernstein et al.), WO90-0130, (Sonic Needle Corp.); EP 316,789 (DonMichael, et al.); DE 3,812,836 (Schubert) and DE 2,438,648 (Pohlman).
The efficacy of any intravascular ultrasonic ablation procedure is inherently dependent upon the ability of the operator to position the ultrasonic ablation device in close spaced relation to occlusive plaque or thrombus so that the ultrasonic energy of the device may successfully ablate the occlusive plaque or thrombus.
One means of facilitating proper advancement and positioning of the ultrasound ablation device or catheter is to initially insert and advance a flexible, radiographically visible, guidewire through the vasculature to a point where the distal tip of such guidewire is immediately adjacent, or actually passing through, the offending plaque or thrombus. Thereafter, the ultrasonic ablation catheter or device may be threaded over the prepositioned guidewire to a point where the therapeutic tip or head of the ultrasound catheter is adjacent or in contact with the occlusive plaque or thrombus. Alternatively, prior to insertion of either the guidewire or the ultrasound catheter, the ultrasound catheter may be advanced over the guidewire such that the distal tip of the guidewire extends slightly out of and beyond the distal end of the catheter. Thereafter, the ultrasound ablation catheter and guidewire may be inserted and advanced together through the vasculature to a point at or near the occlusive plaque or thrombus. Thereafter, the guidewire may be further advanced relative to the ultrasound catheter so as to penetrate or pass through the occlusive plaque or thrombus. Thereafter, the ultrasound catheter may be advanced relative to the guidewire to affect the desired ablation of such occlusive plaque or thrombus.
After the ultrasound catheter has been utilized to ablate the occlusive plaque or thrombus, it may be desirable to extract and remove the previously inserted guidewire. In some cases, it may thereafter be desirable to reinsert the same guidewire or a different guidewire through the ultrasound catheter without requiring retraction or removal of the ultrasound catheter.
In view of the desirability of using an ultrasound catheter in conjunction with a prepositioned guidewire, there exists a need in the art for improved or alternative ultrasonic angioplasty catheter devices which are specifically designed and configured for use with a guidewire. In some situations, it may be desirable to fully extract and remove the guidewire from the catheter after the catheter has been advanced to its operative position at the site of the occlusion. To facilitate such extraction and removal of the guidewire, it is desirable that the distal portion of the guidewire be exteriorized in such a manner as to allow the operator to fully extract or insert a guidewire through the ultrasound catheter.